godot-2d-animation

The saved excerpt is a snapshot from review. The external source remains the complete and most current version.

---
name: godot-2d-animation
description: "Expert patterns for 2D animation in Godot using AnimatedSprite2D and skeletal cutout rigs. Use when implementing sprite frame animations, procedural animation (squash/stretch), cutout bone hierarchies, or frame-perfect timing systems. Trigger keywords: AnimatedSprite2D, SpriteFrames, animation_finished, animation_looped, frame_changed, frame_progress, set_frame_and_progress, cutout animation, skeletal 2D, Bone2D, procedural animation, animation state machine, advance(0)."
---

## NEVER Do

- **NEVER use AnimatedTexture** — This class is deprecated, highly inefficient in modern renderers, and may be removed in future Godot versions. Use AnimatedSprite2D or AnimationPlayer instead.
- **NEVER allow Tweens to fight over the same property** — If multiple Tweens animate the same property, the last one created forcibly takes priority. Always assign your Tween to a variable and call `kill()` on the previous instance before creating a new one.
- **NEVER process kinematic movement outside the physics tick** — If your AnimationPlayer moves a CharacterBody2D, ensure the AnimationPlayer's callback mode is set to Physics. Animating physics bodies during the Idle (render) frame breaks fixed timestep physics interpolation and causes stutter.
- **NEVER use `animation_finished` for looping animations** — The signal only fires on non-looping animations. Use `animation_looped` instead for loop detection.
- **NEVER call `play()` and expect instant state changes** — AnimatedSprite2D applies `play()` on the next process frame. Call `advance(0)` immediately after `play()` if you need synchronous property updates (e.g., when changing animation + flip_h simultaneously).
- **NEVER set `frame` directly when preserving animation progress** — Setting `frame` resets `frame_progress` to 0.0. Use `set_frame_and_progress(frame, progress)` to maintain smooth transitions when swapping animations mid-frame.
- **NEVER forget to cache `@onready var anim_sprite`** — The node lookup getter is surprisingly slow in hot paths like `_physics_process()`. Always use `@onready`.
- **NEVER mix AnimationPlayer tracks with code-driven AnimatedSprite2D** — Choose one animation authority per sprite. Mixing causes flickering and state conflicts.
- **NEVER use paper-thin skeletons for deformation** — 2D meshes require balanced vertex density. If your mesh deforms poorly, increase the vertex count near joints in the Mesh2D editor.

---

## Available Scripts

> **MANDATORY**: Read the script for the pattern you are implementing. Inline recipes that duplicated these scripts were removed — the script is the source of truth.

### Do NOT Load (by scenario)
| Scenario | Load | Do NOT Load |
|----------|------|-------------|
| Single character / player | `one_frame_sync_fix.gd`, `animation_state_sync.gd`, optional `animation_tree_step.gd` / `tween_lifecycle_manager.gd` | `multimesh_swarm_anim.gd`, `gpu_mesh_optimizer.gd` (unless fill-rate profiling demands it) |
| Frame events / hitboxes / SFX sync | `animation_sync.gd` (+ AnimationPlayer method tracks) | Swarm/MultiMesh scripts |
| Squash/stretch game-feel | **MANDATORY** `procedural_squash_stretch.gd` | Inline landing-condition snippets in this skill |
| Cutout / IK limbs | `skeleton_2d_rig_helper.gd` | MultiMesh swarm scripts |
| Shader flash / dissolve on anim | `shader_hook.gd` | — |
| Thousands of bats/fish/props | `multimesh_swarm_anim.gd` (+ docs fish tutorial) | Per-entity AnimatedSprite2D / Tween managers |

### Script index
- [one_frame_sync_fix.gd](scripts/one_frame_sync_fix.gd) — **Golden sync path**: `play()` + `advance(0)` with `flip_h` / property changes.
- [animation_state_sync.gd](scripts/animation_state_sync.gd) — State-driven animation + transition queue.
- [animation_sync.gd](scripts/animation_sync.gd) — Method tracks, signal orchestration, blend-space hooks.
- [animation_tree_step.gd](scripts/animation_tree_step.gd) — `AnimationNodeStateMachinePlayback.travel()`.
- [procedur